Thomas Wyatt was a USMarine who fought in the Pacific Theater of World War II.
He was sent on a top secret mission, codenamed Operation Aurora, to investigate a possible WMD threat being designed by the Japanese and extract a scientist working on it. After successfully finding a way off the island, the WMD is set off, killing Wyatt, the scientist and his squad mates. Apparently, the US government actually knew about the WMD and sent Wyatt and his group on a suicide mission to see the effects of the weapon.
Wyatt can be identified in the final cut-scene of the level Operation Aurora on the submarine. He is the one on the far right holding either a Type 100 SMG or Type 5 rifle. He can also be seen on the beach landing scene as the one looking around nervously. The basic way to identify Wyatt is that he does not speak in the cut-scenes, he has a nearly shaven head and also resembles Aguire.